Blue Moon Diamond Is Likely to Break World Record at Sotheby’s Auction [VIDEO]

In 1905, the world’s largest rough diamond, the 3,106-carat Cullinan, was discovered in South Africa’s mine bearing the same name. Known as the world’s main source for rare blue diamonds, the Cullinan mine was home to another important gemological discovery 109 years later: an extremely rare blue diamond weighing 29.62 carats. Nicknamed the Blue Moon Diamond because of its once-in-a-blue-moon size, color, and clarity, the gemstone was labeled “internally flawless” by the Gemological Institute of America and graded Fancy Vivid Blue—the highest color grade possible for a blue diamond.

The New York jeweler Cora International first purchased the ocean-blue gemstone, taking six months to painstakingly cut and polish the raw stone. Sotheby’s will now offer the 12.03-carat, cushion-cut diamond on November 11 at its Magnificent Jewels and Noble Jewels sale in Geneva. Estimated to rake in between $35 million and $55 million, the sale most likely will surpass the current world record (held by Sotheby’s) for a blue diamond. The record was set last year with the Zoe Diamond (a 9.75-carat Fancy Vivid Blue) selling for more than $32 million. Prior to auction, the Blue Moon Diamond will be on exhibit in London, Hong Kong, and New York.